Conventionally, information display devices (navigation devices) installed in movable bodies, such as vehicles and ships, and for displaying locations of the movable bodies have been known. Patent Document 1 discloses an information display device of such kind, specifically, a display device for displaying a location of the ship on a nautical chart.
Moreover, in Patent Document 1, regarding display modes defining a displaying orientation of the nautical chart, north up, head up (heading up), and course up are disclosed. North up is a display mode in which the north direction is an upward direction of a display screen. Head up is a display mode in which a direction to which the information display device is oriented is the upward direction of the display screen. Course up is a display mode in which a direction of a set course is the upward direction of the display screen.
In Patent Document 1, the method of switching among these display modes is not described. Generally, a method of pressing a menu button or the like to call a menu screen, selecting a menu item, such as display setting, and selecting a desired display mode is adopted.